Plot hole: When Regina gives Principal Duval the Burn Book, she states that there are only three girls in the whole school who aren't in it. Following this scene, as the girls are fighting in the hallways, Principal Duval calls on all the girls in the junior class to the gymnasium. Why would he assume that all the girls in the hallways are juniors seeing as Regina had just told him the Burn Book contained all the girls in the school, not just the juniors?

Cady breaks up her Spring Fling tiara that she receives. On stage, she breaks it up into many pieces and throws them out into the crowds; it is clear that the amount we see being thrown into the crowds is a major amount of pieces - almost too much from just one tiara. However then when she leaves the stage, we see her holding approximately half of the tiara still. This would not be possible from the aforementioned amount that Cady has already snapped off and thrown into the crowd.